A simple optimized amplitude pupil mask for attempting to direct imaging of Proxima b with SPHERE/ZIMPOL at VLT

TL;DR

This paper introduces a simple amplitude pupil mask designed for the SPHERE/ZIMPOL instrument at VLT, which improves contrast for direct imaging of Proxima b by reshaping the PSF and is easy to implement.

Contribution

The paper presents the design, optical simulations, and testing of a novel amplitude pupil mask that enhances contrast at the planet's separation, compatible with existing VLT instruments.

Findings

Contrast at 2λ/D improved by about an order of magnitude.

Mask effectively reshapes the PSF to facilitate direct imaging.

Design is simple and can be integrated into current setups.

Abstract

Proxima b is a terrestrial exoplanet orbiting in the habitable zone of our closest star Proxima Centauri. The separation between the planet and the star is about 40 mas and this is with current instruments only reachable with direct imaging, using a visual extreme AO system like SPHERE/ZIMPOL. Unfortunately, the planet falls under the first airy ring at 2$\lambda$/D in the I band, which degrades achievable contrast. We present the design, optical simulations and testing of an amplitude pupil mask for ZIMPOL that reshapes the PSF, increasing the contrast at $r = 2\lambda$/D about an order of magnitude. The simple mask can be inserted directly into the current setup of SPHERE.